A preferred, but not exclusive, application of the invention is that of measuring the isotopic ratios of gases or of substances that have first been transformed into the gas phase. It is known in this connection for various analyzers to be used, such as for example mass spectrometers (MS), accelerator MS, optical spectrometers (for example laser-resonance measurement), scintillation counters, etc. Preferred analyzers are mass spectrometers, such as for example multi-collector sector-field MS, time-of-flight mass spectrometers (TOF-MS) or quadrupole MS, in particular specifically for the determination of isotopic ratios. The invention is preferably used for measuring methane or respiratory gas, for example, and/or for determining the isotopic ratios of carbon, oxygen, nitrogen, sulfur, phosphorus, water vapor/deuterium or chlorine in suitable or appropriately prepared samples. The following molecules may be measured for this: N2, CO, O2, H2, CO2, N2O, CH4 and/or NO2. This list is not exhaustive.
In the analyzer, simplest possible gases—one- to three-atom gases with only one or two different atoms—are measured. In a specific implementation, gases with more complex molecules may also be analyzed. More complex molecules are generally transformed into simpler molecules before the analysis, by pyrolysis, oxidation and/or reduction. Corresponding reactors or furnaces, or combinations of furnaces, are provided for this purpose.
Starting materials for the analyses are often liquids or gas mixtures, the constituents of which are separated from one another over time in a gas chromatograph.
Altogether, the apparatus used comprising the gas chromatograph, furnaces for gas conversion and the analyzer is quite complex. In particular in the area of gas conversion, the arrangement of the individual component parts of the apparatus can be varied in many ways. A slightly different construction is required for virtually every type of conversion. For the user, this is laborious and susceptible to error.